An eyewitness to the Watertown shootout with the Boston Marathon bombing suspects says an MBTA Transit Police officer may have been hit by "friendly fire."

An eyewitness to the Watertown shootout with the Boston Marathon bombing suspects said an MBTA Transit Police officer may have been wounded by friendly fire.

Officer Richard "Dic" Donohue is recovering at Mount Auburn Hospital from a gunshot wound to his upper right thigh. Doctors said Donohue lost so much blood during the April 19 shootout that he nearly died, but he's now expected to make a full recovery.

Donohue and his partner were among the first officers on scene at the intersection of Dexter Avenue and Laurel Street, where bombing suspects Tamerlan and Dzhokhar Tsarnaev stopped the SUV they allegedly carjacked earlier that night.

At least a dozen officers from four different police agencies engaged in gunfire with the suspects, with about 300 bullets fired in all. The Tsarnaevs also reportedly launched explosives at the police, including at least one bomb similar to the pressure cookers used at the marathon finish line.

Witnesses told the Boston Globe that Donohue appeared to have been wounded near the end of the confrontation, after Tamerlan Tsarnaev was shot and his brother Dzhokhar was driving away.

Jane Dyson lives just 140 feet away from where Donohue went down and provided a statement of what she saw to the Globe.

"A black SUV appeared, and rapid gun fire was focused on the vehicle," Dyson wrote. "It appeared to me that an individual at the corner [of the street] fell to the ground and had probably been hit in the gunfire."

"I later learned that the individual who had been shot was Officer Richard Donohue," Dyson said. Her statement was supported by two other eyewitnesses to the shootout.

State police said the investigation into how Donohue was wounded is still in process, but defended the officers' actions.

"Considering the chaos on those dark streets, where a pair of homicidal terrorists were firing shots and throwing bombs at police, the fact that friendly-fire incidents may have ­occurred detracts nothing, not one bit, from the valor and heroism of the officers and troopers who caught up to them that night," state police spokesman David Procopio told the Globe.

An expert on law enforcement tactics agreed.

"It’s arguably a wartime situation," said Chuck Wexler, executive director of the Police ­Executive Research Forum. "Police agencies are not generally prepared for the kind of wartime situation that these officers encountered."

The Middlesex District Attorney's office is investigating two other possible "friendly fire" incidents from that night. In one, another Transit Police officer was grazed by a bullet; in the third, a Boston vehicle was damaged after an officer shot at it, apparently believing it to be the suspects' SUV.